So I see that the franchise's response to having killed off Han Solo is to offer an upcoming movie about his earlier years. I can't help feeling that this is a mistake, in terms of the artistic integrity of Star Wars. Just as the plot function of Luke Skywalker in the original story was to be raised from backwater obscurity into greatness, the plot function of Han Solo was to be rescued from self-serving irrelevance and made, for the first time in his life, to work for a cause greater than himself. (And Leia? She's the princess. Her function is to be rescued. I don't like that either, but we knew this was an old-fashioned story when we took it.)
It follows that any earlier story of Han's would be just a trivial adventure with no greater significance. You can make a popular movie this way - it worked for Indiana Jones - but it'll feel shoddy. If you try to charge it with significance by making it a turning point and personal revelation for Han the way that the first Star Wars was, you undercut the significance and meaningfulness of that first Star Wars. Now you're saying he already went through that, and either backslid (in which case he could do so again) or else just needed reinforcement. Either supposition trivializes.
Also: Luke, Han, and Leia are a triad. They work best together. This was why Force Awakens didn't work: its treatment of the iconic characters was too fragmented, and, unlike the original movie which was a complete story as well as first of a trilogy, TFA wasn't enough of a complete story to make anything iconic out of Rey, Finn, and Poe (characters I remember so well I actually had to go and look their names up just now).
I suppose the best way to deal with all this for the impending movie would be to make a story that shows how Han became such a cocky bastard in the first place. It still wouldn't have any larger significance, but at least it'd be a complete story with a plot function end point.